What Are Weeds? Any plant we don’t want, at least where they’re growing. There are annual, biennial and perennial weeds. Some of them produce unbelievable amounts of seed from single plants – 15,000 for ragweed, 52,000 for purslane, and so on. Most of the seeds are deposited in the soil, so weed populations increase yearly if they aren’t managed. See what we’re dealing with here?
What’s Wrong With them? They compete with the plants we want for water, light, soil nutrients, and space. And by definition, we don’t like the way they look.
What’s to Like About Them? They stabilize and add organic matter to the soil, while providing some amount of habitat and feed for wildlife. And some of them don’t look all that bad (dandelions DO have their supporters).
- Mulch, 2-3 inches in spring, is the most important weed prevention technique. You can apply it in the fall but make sure there are still 2-3 inches in the spring. Remove as many weeds as possible before applying the mulch.
- Vigilance is key because things just get worse if you let your weeds throw their seeds around. So keeping on top of weeding is really important in preventing more weeds. And if you’re just starting to get a handle on them, remember it’ll be much easier in the second and third years. Really.
- Close spacing of plants helps. Never forget that bare ground is an invitation to weeds. (If you see bare ground, it won’t be bare for long.)
- Landscape fabric is sometimes applied on top of soil to block weed germination while allowing air and water to penetrate, and Bob Peterson (manager of Behnkes Garden Supply Department in Beltsville) is a big fan of the stuff. Click here for a detailed explanation of how to use it or here for good advice from a designer/professional gardener.
- Corn gluten meal actually prevents, rather than kills weeds – see below under Organic Weed-Killers.
All gardens have weeds, period. You can hire someone to do the weeding for you or, if you’re a gardener, you grab a tool and get some exercise. Besides, it goes pretty fast and makes a huge difference in the appearance of the garden, so it’s surprisingly gratifying. (Lots of gardeners actually enjoy weeding – and I’m one of them.)
- Remove all of them, no matter how small they may be, and remove the whole plant, including the roots. Otherwise it’s a waste of time, right?
- If the soil is dry, then water before weeding, or the day before.
Hoes are the old-fashioned, back-saving stand-up tool used by farmers and gardeners since forever. Their flat blades slice through shallow roots but often remove just part of the deeper ones, which then grow back. And the chop/draw motion can take lots of strength and still be hard on the back (though at least the extreme bending over of hand-weeding is avoided).
Hand tools are used by most gardeners I know, maybe because they let us get close to the ground where we can get a good look at our plants. To prevent backaches I stop after 30 minutes of weeding and find something else to do in the garden. Trowels are, for me, the main tool for weeding, especially the pointy one you see in this photo. The point means it’s terrific at digging, and it even measures the depth of the hole you’ve dug — brilliant!
Following the principles of Integrated Pest Management, most gardeners today choose the least toxic tactic first to deal with weeds, which is why I listed tools first. (And who among us couldn’t use the exercise?) But sometimes other tactics are called for – like herbicides.
Bob Peterson recommends two organic herbicides, both with ammoniated salts of fatty acids as the active ingredient. The products are Espoma’s Earth-tone 4n1 Weed Control and Natria Grass and Weedkiller from Bayer, both of which he considers them both safe and effective.
Bob also likes regular water – boiling or as hot as possible – as an organic weedkiller, especially for those hard-to-reach spots like in cracks.
Corn gluten meal is often applied on top of lawns in early spring (when the forsythias are blooming) to prevent the germination of weed seeds – as a “pre-emergent” weedkiller. It’s effective, and has the added benefit of providing all the Nitrogen the lawn needs each year to thrive – provided it’s applied in the right amount. Results will continue to improve in the second and third years. Corn gluten meal is also the active ingredient in the popular product Preen’s Garden Weed Preventer for vegetable and flower gardens.
We’re seeing increased interest in the use of highly concentrated vinegar as an herbicide – as high as 20-25% acetic acid – and indeed it works. Trouble is, concentrations of 11% or more can burn skin and damage corneas. It’s used in commercial applications and by homeowners for pickling and cleaning, as well as killing plants. The EPA prescribes personal protective equipment and staying away from the sprayed area for a full 48 hours. For more about why Behnkes doesn’t sell highly concentrated vinegar, here’s Bob:
None of EPA’s safety information is included on the twist-tie information on the jug of Bradfield Horticultural Vinegar. Because the public is used to thinking of vinegar as something you can safely splash on your salad and eat (household vinegar is typically 5% acetic acid), they are generally unaware of the potential dangers of a higher concentration.
I discourage the use of these products except when nothing else does the job (usually for removal of invasive plants or poison ivy) and only under the right conditions (e.g., no wind, and nowhere near water) and sparingly. Roundup is the most commonly used synthetic herbicide, with the active ingredient glyphosate. Use all herbicides – organic or synthetic – strictly according to the label, okay? Read ‘em; follow ‘em.
Weeds in Lawns
Bob recommends making your lawn as thick as possible so as to not give weed seeds a chance. He writes,
The best weed deterrent in the lawn is a strong canopy of grass. Cut at proper height, build the soil health and micro-biological activity in the soil so the plants can utilize the nutrients in the soil. When you develop healthy grass and weeds become an afterthought. If someone really wants to have the “golf course” lawn they should move to a residence on the golf course. There is nothing wrong with a few weeds in the lawn.
Indeed, organic gardening experts are encouraging us to adapt to imperfect “freedom” lawns that include a few weeds – so think of it as going green with your lawn.
Good Information on Line
- NC State’s huge compilation of weed links.
- Penn State’s Landscape Problem Solver
- Va Tech Weed Identifier and the Rutgers Weed Identifier and the U. of California’s Weed Identifier.